Dust collection in a rotary floor finishing machine

ABSTRACT

In a powered floor finishing machine or surface abrading machine, a housing encloses an abrading component. Dust is collected at the edge of the abrading component by an airflow drawn through the gap between the abrading component and the edge of the housing, through the housing to a suction port and on to a dust collection system. Supplemental air at relatively higher pressure is injected into the housing at a favorable position and angle as to the interior geometry and normal airflow pattern so as to inhibit dust collection within the housing and increase average airflow velocity from the gap to the suction port. Less dust is precipitated out of the airflow before it gets to the suction port, thus improving the efficiency and effectiveness of dust collection, and extending the intervals between which the interior of the housing need be cleaned.

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 61/258,264, filed Nov. 5, 2009. This application is herein incorporated by reference in its entirety for all purposes.

FIELD OF THE INVENTION

This invention relates to floor finishing machines, and more particularly to floor finishing machines equipped with suction ports in their housings connected to vacuum-type dust collection systems and further configured with a pressurized airflow source connected to airflow inlets in the housing.

BACKGROUND OF THE INVENTION

A rotary floor finishing machine, or floor polisher, has a motor mounted atop a housing with its drive shaft extending into the housing, terminated by a triple planetary reduction gear that reduces a motor speed of about 1725-1750 rpm by 11 to 1 down to about 160 rpm. The reduction gear accepts the keyed attachment of a circular “pad-lock”, which is a rigid disk with a bristled bottom that readily grips a circular mat, which in turn readily grips a circular sheet of screen type abrasive floor finishing material. This type of rotary floor finisher, which may be variously referred to as a floor buffer or polisher, configured in this manner with the abrasive screen material, is used to smooth out or “screen” the surface of a hardwood floor surface prior to applying a finish. The machine and screening process creates a significant amount of dust. Dust collection is more important today than in years gone by, due to the heightened awareness of its environmental and health effects, including in particular, potential harm to users' respiratory systems.

One common solution, a simple adaptation to a basic rotary floor machine and to other types of surface contact, materials abrading machines that create a similar dust problem, is to configure or install a suction port somewhere on a main housing that substantially encloses the abrading tool and its motorized motion mechanism to within a minimal distance of the target surface.

The lower edge of the skirt portion of the housing is supported off the target surface by the pad-lock or other abrading mechanism sufficiently high to avoid contact of the hard edge of the housing with the floor or target surface and to permit airflow into the housing through the periphery gap between them. The motion mechanism may be rotary, orbital, a belt system or otherwise in type, configured to scour or scrub the target surface with an abrasive-faced sheet that renders and removes small particles from the face of the target surface and throws it off into the air as dust, proximate the edge of the housing and preferably within the periphery of the enclosing skirt of the housing.

The suction port is connected directly or by a suitable length of flexible hose or other type conduit to a dust collection system, in the case of some rotary floor sanding machines a separate, portable industrial dust collection system. In other embodiments, the dust collection system may be integral to the surface-contact materials abrading machine. The dust collection system typically includes a vacuum source in the form of a powered blower connected to a container or dust repository configured with a dust filtration system upstream of an exhaust port or vent, which acts as a trap for the airborn dust materials. The blower may be upstream of the dust filter in the dust ladened airflow, or more commonly downstream of the dust filter, in the filtered airflow. The blower may be driven by its own motor such as if the dust collection is a separate device, or in some cases by the same motor that drives the abrading motion system.

The suction action of the dust collection system is applied through the hose and port to the housing so that air is drawn into the housing around its periphery, carrying the dust created by the abrading motion into and through the housing into the dust collection system. In this respect, the housing can be considered an extension of the dust collection system On the backend of the dust collection system, the airflow from which most of the dust has been removed and deposited in a dust repository, is ejected by blower pressure to atmosphere. The dust container or repository is emptied from time to time as required. The dust filtration mechanism may be changed or cleaned or otherwise renewed from time to time as required, by any common means including but not limited to simple brushing or shaking, changing of the filtering element, or airstream backflow.

In the specific case of a rotary floor finishing machine with a separate dust collection system connected in the manner described, air is drawn into the housing at floor level through the annular gap around the perimeter of the rotating pad-lock, through the plenum formed by the housing and the pad-lock, into the suction port, and through the hose to the dust collection system.

However, the floor finishing machine used in the screening mode where some abrading of floor surface material is intended and dust is created, with a vacuum system attached and operating, is commonly known to be susceptible of dust accumulation or dust build up on the top of the pad-lock and elsewhere on the interior wall of the housing. This accumulation eventually impedes or clogs the airflow pathway, and requires disassembly and removal of the dust build up.

What is needed, therefore, are techniques for more efficient and effective dust collection in a floor finishing machine.

SUMMARY OF THE INVENTION

Applicant has determined that the rotary floor sander and dust collection system in the commonly used configuration described above may provide adequate air velocity at floor level at the periphery of the pad-lock, beneath the skirt or edge of the housing, to pick up much of the abraded dust material emitted at the edge of the screen and draw it into the plenum created by the housing. But the larger central volume of the plenum or interior space within the housing and above the pad-lock creates a change in airflow velocity. The airflow velocity drops between the edge of the pad-lock and the suction port due to the enlarged cross section area through which it is drawn, and increases again in the reduced cross section area of airflow at or nearer the suction port.

In the slow airflow zone between the high velocity pickup zone and the high velocity suction zone, some of the dust, the heavier particles in particular, precipitates or falls out of the airflow, and does not make it to the suction port. This “dust precipitate” is a major source of the clogging accumulation of dust that builds up within the housing. The buildup creates a growing resistance to airflow and rapidly reduces the effectiveness of the dust collection system.

One embodiment of the present invention provides for injecting supplemental or makeup air into the housing, downstream of the floor level opening and upstream of the suction port, within the airflow volume limits of the dust collection system, which may contribute to stimulating a higher average airflow velocity through the housing above the pad-lock to the suction port than would otherwise be present. The higher velocity airflow through the housing keeps more of the collected dust airborne until it is drawn to and into the suction port. The supplemental air source may be injected with one or more nozzles in such a manner as to impinge on selected surfaces, inhibiting the settling of any dust there and carrying it back into the primary airflow path where it is disposed of as intended. The supplemental air may be delivered from an independent airflow source such as a separate fan or blower.

Supplemental air nozzles may be directed perpendicular to the plane of rotation of the rotating abrading component, or biased at an angle supporting a circular airflow corresponding to the direction of rotation of the rotating component, or conversely, in a direction opposing the direction of rotation so as to optimize the scouring effect of injected airflow on the rotating component, or on the housing wall. The supplemental air may come from several sources. For example, it may be scavenged off the filtered air exhaust outlet of the dust collection system itself. Any convenient source of air may be used, and pressure alone is not critical, so long as the supplemental airflow volume delivered to the housing is controlled so as not to exceed the airflow rate capacity of the collection system and not to negatively impact the dust collection airflow path from floor to suction port or the dust pickup suction power and airflow velocity at floor level.

A suitable pressure and volume of supplemental airflow may be admitted and directed into the housing at a favorable position and angle with respect to the geometry of the interior space available for airflow, so that the airflow from floor to suction port is not subject to a seriously reduced velocity midway in between. By this means, the tendency for dust to accumulate in the housing is reduced, thus improving the efficiency and effectiveness of the dust collection system, and extending the intervals between which the interior of the housing need be cleaned.

In another embodiment of the present invention a suction port may be configured as an annular opening about the central drive shaft or be located outboard of the central driveshaft elsewhere on the housing. Supplemental air inlets and/or their nozzles may be displaced or directed so as to create turbulence and/or enhance airflow velocity in areas of otherwise lower airflow velocity than at the point of initial dust pickup.

The invention, in another embodiment, may be extended to rotary, vibratory, and belt type floor finishers and abrading machinery of all types, where the disk, plate, or belt mechanism is enclosed by a housing and skirt that extends to or nearly to the floor or other target surface being abraded, creating in effect a plenum within the housing around the motion mechanism, where floor or surface covering material is abraded by the rotating, vibrating or rolling motion of the selected abrasive or polishing material to the extent that dust is created.

The dust created may be collected at floor or surface level or around the periphery of the disk or belt contact surface within the skirt of the housing, and drawn up and through the periphery of the open housing, and through the housing interior, to a suction port higher in the housing. The suction port or ports may be piped, plumbed or otherwise in communication with a dust collection system which may be mounted on the machine or be remote to the machine.

The supplemental air source and nozzle of the invention is applicable to any such device or machine where dust collection airflow velocity is subject to significant reduction as it flows from the restricted entry gap at floor or abrading surface level through the relatively larger interior volume of the housing enclosing the abrading mechanism, to the suction port leading to the dust collection system, as a means of improving and extending the dust collection capability of the machine's overall functionality.

The features and advantages described herein are not all-inclusive and, in particular, many additional features and advantages will be apparent to one of ordinary skill in the art in view of the drawings, specification, and claims. Moreover, it should be noted that the language used in the specification has been principally selected for readability and instructional purposes, and not to limit the scope of the inventive subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic view of a floor finishing machine configured with a supplemental air injection system and connected to a separate dust collection system.

FIG. 2 is a diagrammatic top view of another floor finishing machine depicting a drive motor and gearbox centrally mounted on a circular housing, a pair of inlets 180 degrees apart on the top of the housing outboard of the motor for makeup air, and a pair of suction ports on top of the housing outboard of the motor, rotationally displaced 90 degrees from the makeup air inlets.

FIG. 3 is a diagrammatic top view of another floor finishing machine depicting a drive motor and gearbox centrally mounted on a circular housing, with a singular makeup air inlet on the top of the housing outboard of the motor, displaced from a singular suction port on the top of the housing outboard of the motor.

FIGS. 4A, 4B and 4C depict three embodiments of a makeup air inlet nozzle configuration as mounted in the top of a housing, with respect to an enclosed rotating abrading component including its plane and direction of rotation; the nozzle of FIG. 4A being directed perpendicular to the plane of rotation, the nozzle of FIG. 4B being configured at an angle biased against the direction of rotation, and the nozzle of FIG. 4C being configured at an angle biased towards the direction of rotation of the abrading unit.

DETAILED DESCRIPTION

The invention is capable of various embodiments, which may encompass three major components: an abrading machine, a dust collection system, and a supplemental airflow (or air injection) system. What is illustrated and described is intended to be instructive but not limiting of the scope of the invention.

The abrading machine may be a surface contacting, motion-based abrading machine, in this case a rotary type floor finishing machine. The abrading machine may be connected to or configured to be connected to a dust collection system, in this case a separate, free standing dust collection system. The dust collection system generates a suction force within the machine's housing, creating an airflow path from floor or work surface level around the periphery of the abrading component, in this case a rotating pad-lock, between the pad-lock and the lower edge or skirt of the housing in which it is enclosed, through the interior of the housing, into one or more suction ports in the housing wall, and hence to the dust collection system.

The supplemental air source and system for supplying supplemental air to the housing, is in this case a fan or blower device mounted on the floor finishing machine and connected by an air line to an inlet on the housing, although in other embodiments it may be separate from the abrading machine, and integral or separate from the dust collection system, being connected to the abrading machine only by the air line.

The first abrading machine and dust collection system typically require a power source, which may be separate or shared. The dust collection system will generate negative pressure within the housing, with respect to ambient pressure. The supplemental air system may or may not be powered for pressurization above atmosphere, depending on the amount of pressure differential desired between plenum pressure and supplemental air pressure or injection pressure. The scouring effect of injection air on surfaces is enhanced by higher excess pressure, while the enhancement of airflow velocity is less dependent on excess pressure and more on the added volume of supplemental air. Other and numerous variations in the configuration of these three major components and their respective details of construction and design are within the scope of the invention.

Referring now to the embodiment of FIG. 1, floor finishing machine 1 is connected to dust collection 2, and is configured with a supplemental air injection system 3. In more detail, the floor finishing machine 1 has a housing 10, upon which is centrally mounted a motor 12. The motor shaft extends to and rotates pad-lock 14 within housing 10. Rotation of the pad-lock and selected pads that may be applied or attached to it causes an abrading action on the floor surface to which it is applied. The rotating action causes the abraded material to be thrown off as dust at the edge of the pad-lock. Dust collection system 2, powered by blower 28, creates an airflow that draws air ladened with at least some of the emitted dust through gap 20 between pad-lock 14 and the lower edge of housing 10, through plenum 22 defined by housing 10 and the enclosed rotary components, into suction port 24, through conduit 26, and into dust collection receptacle 27 where it is filtered from the air and collected. The filtered air is exhausted to atmosphere.

Supplemental air injection system 3 includes a motorized fan 38, mounted in this embodiment on the side of motor 12, which provides a calibrated or metered amount of supplemental air through air line 36, through inlet 34, to be injected by nozzle 32 into plenum 22.

It will be apparent that the volume of airflow through suction port 24 is the sum of the periphery airflow through gap 20 and the supplemental airflow injected at nozzle 32. The volume supplemental airflow delivered to the plenum must always be less than the volume of airflow drawn through section port 24, or airflow through gap 20 is negative and no dust will be collected.

Referring now to FIGS. 2 and 3, the air inlets and suction ports may be variously configured on a housing. In FIGS. 2 and 3, housing 10 of a rotary type floor finishing machine is equipped with one or more suction ports 24 connectable by a conduit to a dust collection system. A supplemental or makeup air source, which may be in the form of a fan or blower mounted on or near the floor finishing machine and connected by an airline to housing 10 as in the embodiment of FIG. 1, has one or more nozzles 32 installed at respective inlets 34.

The two inlets 34 of FIG. 2 are installed in the top of housing 10, displaced radially 180 degrees from each other, although in other embodiments there may be more or fewer inlets, configured uniformly or otherwise with respect to one another. The two suction ports 24 in the deck or top of housing 10 are similarly 180 degrees radially displaced from each other, and 90 degrees displaced from inlets 34. The embodiment of FIG. 3 illustrates one suction port 24 and one air inlet 34 mounted atop housing 10, outboard of motor 12, and displaced from each other radially. Functionally, it performs similarly to the embodiment of FIG. 2.

In both embodiments, supplemental air injected at inlets 34 adds volume and velocity to the airflow in the central portion of the plenum defined by the housing and the rotating components within, between the point of dust intake at floor level and the suction port in the top of the housing. This offsets the normal drop in velocity that occurs in that region, and promotes carriage of more of the dust in the airflow to the suction port and hence to the collection system. In other words, the force and volume of the injected air, in addition to the air and dust drawn in at floor level, promotes turbulence and higher average velocity of airflow in the plenum, tending to keep the collected dust airborne until it reaches the suction port where the cross section of the airflow path is reduced and airflow velocity is greatest.

The supplemental air volume added to the housing for maintaining airflow velocity through the housing is one aspect of the invention. Referring now to FIGS. 4A, 4B, and 4C, the makeup air nozzle configuration and inlet pressure can be in the form of a relatively open nozzle of relatively lower air pressure or more of a smaller diameter, higher pressure air jet. The makeup air nozzle can be arranged to have injected airflow impinge on the wall of the housing, or as illustrated in FIG. 4A, perpendicular to the plane of the pad-lock so as to have airflow impinge on the top of the pad-lock, inhibiting the settling of dust at that location.

Referring to FIGS. 4B and 4C, the nozzle can alternatively be oriented at any angle off the perpendicular towards or opposite the direction of rotation or radially inboard or outboard from the axis of rotation of pad-lock 14 up to parallel with the plane of rotation. The direction of rotation of the pad-lock is indicated by the solid arrow as one example for illustrative purposes. Supplemental air injected at an angle biased against or opposing the direction of rotation as in FIG. 4B impinges on the pad-lock with a scouring, uplifting action so as to inhibit the settling of dust thereon. Supplemental air injected at an angle biased towards the direction of rotation as in FIG. 4C can both impinge on the pad-lock so as to inhibit the settling of dust thereon, while also enforcing the circular airflow within the housing consistent with the direction of rotation of the pad-lock 14, enhancing airflow velocity within the housing and sustaining the suspension dust in the airstream. There may be more than one nozzle at a respective inlet. Different nozzles may have the same or different angular orientations. The pad-lock may rotate in either direction.

In other embodiments, the housing may be terminated at the lower edge with a perimeter brush extending to floor level. The brush helps contain dust emissions to within the annular region or gap 20, and increase airflow velocity at floor level due to the restriction of the opening between the housing and the floor, for optimal lifting of the emitted dust without harming the floor.

Details among embodiments can vary considerably. For example, injection of supplemental air may be limited to the controlled admission of outside air at atmospheric pressure, no further pressurization needed, through the one or more air inlets into the housing where the dust collection system maintains a lower-than-atmosphere pressure for suction. Nozzles may be limited to mere openings at appropriate locations in the housing, or they may extend as one or more tubes from the housing wall or other manifold into the interior of the housing, to positions where the injection of supplemental air is most beneficial to maintaining airflow velocity through the housing, thus keeping the dust suspended and moving.

In all cases, make up air must not be injected into the housing at a rate so high that it will exceed the suction power and airflow capacity of the suction port and dust collection system, or even so much as to reduce the suction power or airflow volume and velocity at the floor level around the pad-lock below that amount required to effectively pick up the dust initially and draw it into the housing.

With respect to new machine design or retrofitting existing machines already equipped with suction based dust collection systems, the optimal range of makeup air pressure, volume, and nozzle configuration may be determined empirically for particular models and combinations of abrading machinery and dust collection systems. In new or retrofit systems, the source of supplemental air may be independent, or be directly or indirectly provided by the abrading machine itself from its own motor and air cooling system or by the dust collection system, such as by its motor and air cooling system or by scavenging filtered exhaust air.

The invention is capable of other and various embodiments. For example, there is within the scope of the invention, a powered, motion-based, surface abrading machine comprising a housing within which a powered motion mechanism moves an abrasive element with respect to a target surface whereby dust is emitted at the periphery of the abrasive element, the housing being configured with at least one suction port, the suction port communicating with a dust collection system configured to transport the dust in an airflow drawn through a periphery gap between the abrasive element and an edge of the housing, through the housing to the suction port, and hence to the dust collection system, and a supplemental air source communicating with an air inlet in the housing through which supplemental air is injected into the housing between the periphery gap and the suction port. There may be at least one or more supplemental air nozzles attached to the air inlet and configured to terminate at a selected position and angle of orientation within the housing so as to increase airflow velocity between the periphery gap and the suction port. The machine may be configured to inject supplemental air into the housing at a pressure and volume high enough to increase minimum airflow velocity in the housing between the periphery gap and the suction port while maintaining dust supporting airflow in the periphery gap, and at a volume less than the maximum airflow volume capacity of the dust collection system.

Another embodiment of the invention is in the form of a rotary floor finishing machine comprising a housing within which rotates a pad-lock, the housing being configured with at least one suction port, the suction port communicating with a dust collection system configured for transporting dust in an airflow drawn through an annular gap between the pad-lock and a lower edge of the housing, through the housing to the suction port, and hence to the dust collection system, and a supplemental air source communicating with an air inlet in the housing through which supplemental air is injected into the housing between the annular gap and the suction port. There may be at least one or more supplemental air nozzles attached to each air inlet and configured to terminate at a selected position and angle of orientation within the housing so as to increase airflow velocity between the annular gap and the suction port. The selected angle of orientation may have a bias towards or away from the direction of rotation of the pad-lock. The inlet may be displaced from the suction port. The supplemental air source may be configured to provide supplemental air of at least ambient pressure.

The housing and/or the pad-lock may incorporate vertical extensions and/or interior spacers or filler components whereby the interior volume between the housing and the pad-lock is selectively enlarged or reduced so that the airflow path between the gap and the suction port is otherwise improved and the airflow velocity better maintained. The machine in these or other embodiments may incorporate a brush skirt extending from the edge of the housing to the floor.

In yet other embodiments, the nozzles may be configured to inject the supplemental air so as to impinge on a selected surface of the housing or the pad-lock. The machine may be configured to inject supplemental air into the housing at a pressure and volume high enough to increase minimum airflow velocity in the housing between the annular gap and the suction port while maintaining dust supporting airflow in the annular gap, and at a volume less than the maximum airflow volume capacity of the dust collection system.

The invention is also susceptible to methods for collecting and containing dust when using a rotary floor finishing machine. For example, a first mode is providing a housing within which a powered motion mechanism moves an abrasive element with respect to a target surface whereby dust is emitted at the periphery of the abrasive element, the housing being configured with at least one suction port, the suction port communicating with a dust collection system configured to transport the dust in an airflow drawn through a periphery gap between the abrasive element and an edge of the housing, through the housing to the suction port, and hence to the dust collection system. A second mode is providing a supplemental air source communicating with an air inlet in the housing through which supplemental air is injected into the housing between the periphery gap and the suction port. There may be provided at least one or more supplemental air nozzles attached to the air inlet and configured to terminate at a selected position and angle of orientation within the housing so as to increase airflow velocity between the periphery gap and the suction port. Supplemental air may be injected into the housing at a pressure and volume high enough to increase minimum airflow velocity in the housing between the periphery gap and the suction port while maintaining dust supporting airflow in the periphery gap, and at a volume less than the maximum airflow volume capacity of the dust collection system.

The foregoing description of the embodiments of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of this disclosure. It is intended that the scope of the invention be limited not by this detailed description, but rather by the claims appended hereto. 

1. A powered, motion-based, surface abrading machine comprising: a housing within which a powered motion mechanism moves an abrasive element with respect to a target surface whereby dust is emitted at the periphery of the abrasive element, the housing being configured with at least one suction port, the suction port communicating with a dust collection system configured to transport the dust in an airflow drawn through a periphery gap between the abrasive element and an edge of the housing, through the housing to the suction port, and hence to the dust collection system; and a supplemental air source communicating with an air inlet in the housing through which supplemental air is injected into the housing between the periphery gap and the suction port.
 2. The powered, motion-based, surface abrading machine of claim 1, comprising at least one supplemental air nozzle attached to said air inlet and configured to terminate at a selected position and angle of orientation within the housing so as to increase airflow velocity between the periphery gap and the suction port.
 3. The powered, motion-based, surface abrading machine of claim 1, configured to inject supplemental air into the housing at a volume high enough to increase minimum airflow velocity in the housing between the periphery gap and the suction port while maintaining dust supporting airflow in the periphery gap, and at a volume less than the maximum airflow volume capacity of the dust collection system.
 4. A rotary floor finishing machine comprising: a housing within which rotates a pad-lock, the housing being configured with at least one suction port, the suction port communicating with a dust collection system configured for transporting dust in an airflow drawn through an annular gap between the pad-lock and a lower edge of the housing, through the housing to the suction port, and hence to the dust collection system; and a supplemental air source communicating with an air inlet in the housing through which supplemental air is injected into the housing between the annular gap and the suction port.
 5. The rotary floor finishing machine of claim 4, comprising a least one supplemental air nozzle attached to said air inlet and configured to terminate at a selected position and angle of orientation within the housing so as to increase airflow velocity between the annular gap and the suction port.
 6. The rotary floor finishing machine of claim 5, the selected angle of orientation comprising a bias towards the direction of rotation of the pad-lock.
 7. The rotary floor finishing machine of claim 5, the selected angle of orientation comprising a bias opposing the direction of rotation of the pad-lock.
 8. The rotary floor finishing machine of claim 5, the inlet being displaced from the suction port.
 9. The rotary floor finishing machine of claim 5, the supplemental air source configured to provide supplemental air of at least ambient pressure.
 10. The rotary floor finishing machine of claim 5, the housing and the pad-lock incorporating vertical extensions whereby the interior volume between the housing and the pad-lock is enlarged.
 11. The rotary floor finishing machine of claim 5, further incorporating a brush skirt extending from the edge of the housing to the floor.
 12. The rotary floor finishing machine of claim 6, the nozzle configured to inject the supplemental air so as to impinge on a selected surface of the housing.
 13. The rotary floor finishing machine of claim 6, the nozzle configured to inject the supplemental air so as to impinge on a selected surface of the pad-lock.
 14. The rotary floor finishing machine of claim 6, the nozzle configured whereby injected supplemental air accelerates airflow within the housing in the direction of rotation of the pad-lock.
 15. The rotary floor finishing machine of claim 5, configured to inject supplemental air into the housing at a pressure and volume high enough to increase minimum airflow velocity in the housing between the annular gap and the suction port while maintaining dust supporting airflow in the annular gap, and at a volume less than the maximum airflow volume capacity of the dust collection system.
 16. A method for collecting and containing dust when using a rotary floor finishing machine comprising: providing a housing within which a powered motion mechanism moves an abrasive element with respect to a target surface whereby dust is emitted at the periphery of the abrasive element, the housing being configured with at least one suction port, the suction port communicating with a dust collection system configured to transport the dust in an airflow drawn through a periphery gap between the abrasive element and an edge of the housing, through the housing to the suction port, and hence to the dust collection system; and providing a supplemental air source communicating with an air inlet in the housing through which supplemental air is injected into the housing between the periphery gap and the suction port.
 17. The method of claim 16, further comprising: providing at least one supplemental air nozzle attached to said air inlet and configured to terminate at a selected position and angle of orientation within the housing so as to increase airflow velocity between the periphery gap and the suction port.
 18. The method of claim 16, further comprising: injecting supplemental air into the housing at a volume high enough to increase minimum airflow velocity in the housing between the periphery gap and the suction port while maintaining dust supporting airflow in the periphery gap, and at a volume less than the maximum airflow volume capacity of the dust collection system. 